During the past year, the Retroviral Diseases Section has conducted research on AIDS-related malignancies and also on HIV disease. Much of the work on AIDS-related malignancies has focused on tumors associated with Kaposi's sarcoma-associated herpesvirus (KSHV), also called human herpesvirus-8 (HHV-8). We have found that hypoxia can activate latent KSHV to undergo lytic replication and that several genes of KSHV are specifically upregulated by hypoxia. Two of these genes are Rta and viral Bcl-2. We had previously found that a gene of unknown function, ORF34, is specifically activated by hypoxia. ORF34 is part of a cluster of genes (ORF34 to 37). We have dissected the molecular structure of this gene cluster and its upregulation by hypoxia. One of these genes, ORF36, can phosphorylate ganciclovir, and activation of this gene by hypoxia may be able to be used to therapeutic benefit in KSHV-associated tumors, especially PEL. In addition, we have found that a KSHV-encoded thymidine kinase (ORF21) is upregulated inKSHV-infected cells exposed to hypoxia. This gene can phosphorylate zidovudine (AZT) to a form that is toxic for cells. We have also found that certain drugs used to treat Kaposi's sarcoma (KS), such as doxorubicin, can activate the virus. We are also conducting several clinical trials to bring these discoveries into the clinic and explore other novel approaches to HIV-associated tumors. We have found that the cytokine IL-12 has long-acting activity in KS have also conducted a trial to study the combination of IL-12 and a liposomal anthracycline in patients with advanced KS. We are also studying antibody to VEGF (bevacizumab) as a therapeutic agent in KS. We have initiated trials to study the natural history of multicentric Castleman's disease (MCD), which is also caused by KSHV and plan to explore a therapeutic strategy in this disease involving antiviral drugs activated by KSHV. We have also recently initiated a trial studying novel approaches involving KSHV gene activation and then cytotoxic chemotherapy in primary effusion lymphoma (PEL). We are also studying infusional chemotherapy as therapy for AIDS-associated lymphoma in collaboration with the Metabolism Branch. Finally, we have initiated a clinical trial of BAY 43-906, an inhibitor of Raf kinase and VEGFR3, in patients with KS. With regard to HIV, we have been focusing on two areas: the HIV protease and developing an immune response to peptide sequences that confer resistance to anti-HIV drugs. Our group previously found that glutathiolation of a conserved cysteine at the HIV protease dimmer interface (Cys 95) abolishes HIV-1 protease activity. HIV virions with mutations of Cys 95 have been generated and we are studying the effects that these mutations have on the fitness of HIV under varying conditions. We have recently found that nearly all retroviral proteases are regulated by oxidizable amino acids at the dimer interface and that in the case of HIV-1, this occurs by interfering with dimer formation. This work on HIV protease has identified the dimer interface as a potential therapeutic target, and we have focused on the dimer interface as a novel target. We showed that a peptide could be designed that interfered with HIV protease dimerization and that this peptide could block HIV viral production from infected cells. We have also been exploring the possibility of designing a peptide vaccine to HIV that could induce an immune response to a viral sequence that confers resistance to an HIV drug. In collaboration with Dr. Jay Berzofsky, we have engineered such an peptide that can induce a response against the M184V sequence of HIV reverse transcriptase that confers resistance to lamivudine, and have initiated a clinical trial to explore this as a therapeutic vaccine.